[X86] combineConcatVectorOps - use isSplatValue helper instead of matching specific VBROADCAST opcodes. (#129556)

Author: RKSimon

llvm/lib/Target/X86/X86ISelLowering.cpp

@@ -57798,19 +57798,18 @@ static SDValue combineConcatVectorOps(const SDLoc &DL, MVT VT,
         Op0.getOperand(0).getValueType() == VT.getScalarType())
       return DAG.getNode(X86ISD::VBROADCAST, DL, VT, Op0.getOperand(0));
 
-    // concat_vectors(extract_subvector(broadcast(x)),
-    //                extract_subvector(broadcast(x))) -> broadcast(x)
+    // concat_vectors(extract_subvector(splat(x)),
+    //                extract_subvector(splat(x))) -> splat(x)
     // concat_vectors(extract_subvector(subv_broadcast(x)),
     //                extract_subvector(subv_broadcast(x))) -> subv_broadcast(x)
     if (Op0.getOpcode() == ISD::EXTRACT_SUBVECTOR &&
         Op0.getOperand(0).getValueType() == VT) {
       SDValue SrcVec = Op0.getOperand(0);
-      if (SrcVec.getOpcode() == X86ISD::VBROADCAST ||
-          SrcVec.getOpcode() == X86ISD::VBROADCAST_LOAD)
-        return Op0.getOperand(0);
+      if (DAG.isSplatValue(SrcVec, /*AllowUndefs*/ false))
+        return SrcVec;
       if (SrcVec.getOpcode() == X86ISD::SUBV_BROADCAST_LOAD &&
           Op0.getValueType() == cast<MemSDNode>(SrcVec)->getMemoryVT())
-        return Op0.getOperand(0);
+        return SrcVec;
     }
 
     // concat_vectors(permq(x),permq(x)) -> permq(concat_vectors(x,x))